1. Field of the Invention
The present invention relates to a magnetic recording medium especially a magnetic recording tape used for sound-recording picture-recording or recording in a computer, which is prepared by coating a magnetic composition of a magnetic powder and a binder on a base film. More particularly, it relates to a magnetic recording medium which improves wow and flutter in the reproducing or the recording and reproducing operation after storage of the magnetic recording medium at high temperature.
2. Description of the Prior Art
When a magnetic recording tape is applied in a recording-reducing device such as a cassette deck, the magnetic recording tape runs in contact with a magnetic head and tape guides. Therefore, it is usually required to have a low friction and to maintain the smooth and stable running characteristic. However, the running characteristics of the magnetic recording tape is remarkably inferior at the part of the tape near the core in the running of the tape especially in the running after storage of the tape at relatively high temperature. Thus, the wow and flutter is inferior.
Recently, the magnetic recording tape has been developed and an audio cassette tape has been used not only in room but also in outdoor. For example, when an audio cassette tape is placed in a car parked in sunshine in summer, it is stored at high temperature for a long time. The wow and flutter in the reproducing or the recording and reproducing operation after the storage at high temperature is serious problem. It has been considered the wow and flutter is deteriorated by tackiness of the magnetic layer caused by blooming of a nonionic surfactant or an anionic surfactant admixed with a magnetic powder and a binder or plasticization of the magnetic layer.
The nonionic surfactant or the anionic surfactant has been incorporated to improve the dispersibility of the magnetic powder in the blending of the magnetic powder and the binder, whereby magnetic characteristics of suquareness ratio and Br of the magnetic recording tape are improved. The blooming of the nonionic surfactant or the anionic surfactant or the plasticization of the magnetic layer can be reduced to improve the wow and flutter by reducing the amount of the nonionic surfactant or the anionic surfactant. On the other hand, the magnetic characteristics as the magnetic recording tape are inferior.